Device and method for combining coherent laser beams, and laser system

Abstract

The invention relates to a device for combining coherent laser beams (102) in order to form at least one combined laser beam (104), comprising a phase adjusting device (112) for adjusting a respective phase difference between the coherent laser beams (102), an amplification device (120) for amplifying the coherent laser beams (102), said amplification device (120) coupling out amplified coherent laser beams (124), and a measuring device (138) for ascertaining phase differences (Δφ) between the amplified coherent laser beams (124), wherein the measuring device (138) is designed to measure a respective phase difference (Δφ) between one of the amplified coherent laser beams (124) and another amplified coherent laser beam of the amplified coherent laser beams (124) or between one of the amplified coherent laser beams (124) and at least one reference laser beam (149) in order to ascertain the phase difference (Δφ) between the amplified coherent laser beams (124).

Description

[0001] Device and method for combining coherent laser beams, laser system

[0002] The invention relates to a device and a method for combining coherent laser beams into at least one combined laser beam.

[0003] Furthermore, the invention relates to a laser system.

[0004] From DE 10 2020 201 161 A1 a device for combining a plurality of coherent laser beams is known, comprising a splitting device for splitting an input laser beam between the plurality of coherent laser beams, a plurality of phase adjusting devices for adjusting a respective phase of one of the coherent laser beams, and a beam combining device for combining the coherent laser beams emanating from a plurality of raster positions of a raster arrangement to form at least one combined laser beam, wherein the beam combining device has a microlens arrangement with exactly one microlens array for forming the at least one combined laser beam.

[0005] From US 9,134,538 B1 a system for coherently combining a plurality of optical beams is known, comprising a resonant cavity, a plurality of gain elements arranged within the resonant cavity, a beam combining element in optical communication with the gain elements for coherently combining the optical beams into a coherent output beam, a sensor in optical communication with the beam combining element for detecting at least a portion of the coherent output beam and providing a feedback signal representative of the at least a portion of the coherent output beam, and a phase controller coupled to the sensor for adjusting a phase of at least one of the optical beams based on the feedback signal.

[0006] From WO 2017 / 125345 A1, a phase control system for controlling the relative phase of two laser beams to be coherently combined in a laser system which is intended to provide a phase-controlled sum laser beam is known.

[0007] The invention is based on the object of providing a device and a method as mentioned above, by means of which a combination of coherent laser beams with increased temporal and / or spatial dynamics can be realized.

[0008] This object is achieved according to the invention in the device mentioned at the outset in that the device comprises a phase adjustment device for setting a respective phase difference between the coherent laser beams, an amplification device for amplifying the coherent laser beams, wherein amplified coherent laser beams are coupled out of the amplification device, and a measuring device for determining phase differences between the amplified coherent laser beams, wherein the measuring device is designed to measure a phase difference between one of the amplified coherent laser beams and another of the amplified coherent laser beams or between one of the amplified coherent laser beams and at least one reference laser beam in order to determine the phase differences between the amplified coherent laser beams.

[0009] This allows, in particular, phase differences between the existing amplified coherent laser beams to be measured in pairs. From this, the respective phase differences and / or phase positions for all existing amplified coherent laser beams can be determined in a technically simple manner. This enables effective, precise, and rapid detection of the respective phase differences between the amplified coherent laser beams and thus effective control of the phase differences. With the device according to the invention, phase differences between the existing coherent laser beams can be measured with a high temporal resolution. For example, the time period with which the respective phase difference between the amplified coherent laser beams can be resolved is at most 3 ps, preferably at most 1 ps, and particularly preferably at most 0.01 ps.In particular, the time duration of the measurement of the respective phase difference is in the order of magnitude of a reciprocal of a modulation frequency of the phase adjustment device.

[0010] For example, a measurement accuracy frequency with which the respective phase difference between amplified coherent laser beams can be resolved is at least 0.3 MHz and / or at most 1 GHz and in particular at most 100 MHz.

[0011] Due to the high temporal resolution of the phase difference measurement, the coherent laser beams can be combined with high temporal and / or spatial resolution to form different combined laser beams. This enables, for example, rapid variation of beam distributions and / or pulse parameters, which in turn enables the processing of workpieces at increased speed and with increased temporal and / or spatial resolution.

[0012] In particular, the measuring device is used to determine the phase differences for all existing amplified coherent laser beams and / or pairwise between all existing amplified coherent laser beams. In particular, the measuring device is used to determine the respective phase differences for all possible combinations of the existing amplified coherent laser beams.

[0013] In particular, it is provided that the measuring device measures a respective phase difference between the amplified coherent laser beams before they are combined into at least one combined laser beam. The coherent laser beams can be pulsed laser beams or continuous-wave laser beams. In particular, the coherent laser beams are ultrashort pulse laser beams.

[0014] The device is particularly configured to combine the amplified coherent laser beams into the at least one coherent laser beam. The coherent laser beams and / or the amplified coherent laser beams are, in particular, each laser beam intended to be combined into the at least one combined laser beam.

[0015] The at least one reference laser beam is, in particular, a laser beam intended to measure respective phase differences between this laser beam and the amplified coherent laser beams. In particular, the at least one reference laser beam does not contribute to the combination of the amplified coherent laser beams into the at least one combined laser beam, and / or the at least one reference laser beam is not combined into the at least one combined laser beam.

[0016] The at least one reference laser beam can, for example, be a portion of an input laser beam provided by a laser source, from which one or more of the coherent laser beams are formed. It is also possible for the at least one reference laser beam to be one of the coherent laser beams and / or amplified coherent laser beams.

[0017] The amplification device may, for example, comprise fiber amplifiers, slab amplifiers, rod amplifiers or disc amplifiers.

[0018] It can be provided that the amplifying device has a frequency conversion stage or that a frequency conversion stage of the device is assigned to the amplifying device.

[0019] In particular, a respective phase difference between the coherent laser beams and / or between the amplified coherent laser beams can be adjusted by means of the phase adjustment device. For the aforementioned reason, it may be advantageous if the measuring device is configured to measure phase differences between combinations of two different amplified coherent laser beams or to measure phase differences between different combinations of one of the amplified coherent laser beams and the at least one reference laser beam.

[0020] Different combinations are understood to mean combinations in which both laser beams of the combination are different. For example, within the meaning of this application, two different combinations can be formed from three laser beams.

[0021] It can be advantageous if the measuring device is implemented at least in part as a photonic integrated circuit. In particular, one or more parts or regions of the measuring device, such as a beam guide for the amplified coherent laser beams, are implemented as a photonic integrated circuit. The measuring device can be highly complex due to a large number of measuring units and / or measuring elements and the associated beam guide. By implementing the measuring device as a photonic integrated circuit, the measuring device can be designed in a technically simple manner. In particular, this allows the measuring device to be implemented with a reduced number of individual components.

[0022] In particular, N coherent laser beams and / or N amplified coherent laser beams are provided, wherein the measuring device is configured to measure a phase difference for Nl different combinations of two of the N amplified coherent laser beams or to measure a phase difference for N different combinations of one of the N amplified coherent laser beams and the at least one reference laser beam.

[0023] It may be advantageous if a phase difference is measured between a first of the amplified coherent laser beams and exactly one further of the amplified coherent laser beams, wherein the first of the amplified coherent laser beams is different in all measurements, and wherein exactly one further of the amplified coherent laser beams is different in all measurements or wherein exactly one further of the amplified coherent laser beams is the same in a subset of the measurements or in all measurements.

[0024] In each pairwise measurement, exactly one of the additional amplified coherent laser beams is a different amplified coherent laser beam from the first of the amplified coherent laser beams. Thus, no phase differences are measured between the same amplified coherent laser beams.

[0025] For the same reason, it may be advantageous to measure a phase difference between one of the amplified coherent laser beams and the at least one reference laser beam, whereby the amplified coherent laser beam is different in all measurements.

[0026] It can be provided that at least one measuring group of the first type and / or at least one measuring group of the second type are formed, by means of which phase differences between a first of the amplified coherent laser beams and exactly one further of the amplified coherent laser beams are measured, wherein the first of the amplified coherent laser beams is different in all measurements and wherein in the at least one measuring group of the first type the exactly one further of the amplified coherent laser beams is different in all measurements and wherein in the at least one measuring group of the second type the exactly one further of the amplified coherent laser beams is the same in all measurements.

[0027] In particular, the device may comprise an output device for partially outputting the amplified coherent laser beams, wherein partially outputted amplified coherent laser beams are fed to the measuring device in order to measure a respective phase difference between the amplified coherent laser beams. This allows, in particular, the phase differences of the amplified coherent laser beams to be determined before they are combined to form the at least one combined laser beam. A partial output is understood, in particular, to mean the output of a respective portion and / or beam portion of the amplified coherent laser beams.

[0028] In particular, an intensity and / or a power of the proportionally coupled out amplified coherent laser beams is less than 10% of an intensity or power of amplified coherent laser beams incident on the coupling device.

[0029] It can be provided that the at least one reference laser beam is coupled into the measuring device by means of the coupling-out device, wherein in particular a proportion of at least 90% and / or of at least approximately 100% of the at least one reference laser beam is then coupled into the measuring device 138.

[0030] It is also possible in principle for the at least one reference laser beam to be coupled into the measuring device by means of a separate beam path, which in particular does not lead through the decoupling device.

[0031] The output coupling device is arranged, in particular, in a beam path of the amplified coherent laser beams. For example, the output coupling device is arranged downstream of the amplification device and / or upstream of a combination device of the device with respect to a main propagation direction of the coherent laser beams and / or the amplified coherent laser beams.

[0032] The fact that a first device and / or a first element of the apparatus is arranged downstream of a second device and / or a second element of the apparatus with respect to the main propagation direction is to be understood in the present case as meaning that the coherent laser beams or amplified coherent laser beams first strike the second device and / or the second element and subsequently the first device and / or the first element. The second device and / or the second element is then arranged upstream of the first device and / or the first element. For the proportional coupling out of the amplified coherent laser beams, the coupling-out device comprises, for example, a partially reflecting mirror element and / or a polarization beam splitter element and / or a fiber-based Y-splitter.

[0033] In particular, each of the coherent laser beams is proportionally decoupled by means of the decoupling device and fed to the measuring device.

[0034] It may be advantageous if, by means of the measuring device for measuring the respective phase difference between the amplified coherent laser beams, a portion of one of the amplified coherent laser beams is spatially superimposed on a portion of another of the amplified coherent laser beams, or a portion of one of the amplified coherent laser beams is spatially superimposed on the at least one reference laser beam. In particular, a spatial superposition of the amplified coherent laser beam with the further amplified coherent laser beam or with the at least one reference laser beam occurs collinearly. Due to the particularly collinear spatial superposition of respective portions of the amplified coherent laser beams, their phase differences can be determined by a technically simple intensity measurement, wherein in particular no image processing is necessary.

[0035] A collinear superposition of laser beams is understood in particular to mean that they are superimposed at the measuring device with at least approximately parallel and / or coincident beam axes, with the collinear superposition occurring in particular at the respective measuring elements of the measuring device. For example, the collinear superposition occurs in a common waveguide.

[0036] In particular, the measuring device measures the intensities of spatial superpositions, and in particular collinear spatial superpositions, of two of the amplified coherent laser beams. The measuring device comprises, for example, several measuring units, with one of the amplified coherent laser beams and another of the amplified coherent laser beams being coupled into each measuring unit.

[0037] A measuring unit of the measuring device comprises at least one measuring element for measuring the intensity of a spatial superposition of the two amplified coherent laser beams. The measuring element is designed, for example, as a photodetector or comprises a photodetector. The photodetector can be, for example, a fast photodetector and / or a clocked photodetector and / or a photodiode.

[0038] In particular, N coherent laser beams and / or N amplified coherent laser beams are provided, wherein the measuring device has at least Nl measuring units which are each configured to measure a phase difference between one of the N amplified coherent laser beams and a further one of the N amplified coherent laser beams, or wherein the measuring device has at least N measuring units which are each configured to measure a phase difference between one of the N amplified coherent laser beams and the at least one reference laser beam.

[0039] In one embodiment, at least one measuring unit is provided which has a single measuring element, wherein at the measuring element one of the N amplified coherent laser beams is spatially superimposed with another of the N amplified coherent laser beams or with the at least one reference laser beam, and wherein the measuring device is configured to supply the measuring element and / or the measuring unit with a plurality of pairs consisting of a laser pulse of one of the N amplified coherent laser beams and a laser pulse of the other of the N amplified coherent laser beams or of the at least one reference laser beam, wherein the pairs are supplied to the measuring element and / or the measuring unit with a defined time offset.

[0040] It can be provided that each measuring unit of the measuring device has a single measuring element. In particular, the different pairs, which are fed to the measuring element and / or the measuring unit with a defined time offset, each have a different offset phase difference.

[0041] In particular, an offset phase difference is understood to mean a preset and / or predefined phase difference between two amplified coherent laser beams, and in particular between respective laser pulses of these amplified coherent laser beams. The offset phase difference is, in particular, an additional phase difference to an already existing one.

[0042] In particular, a pair of laser pulses is understood to mean a spatial superposition of two laser pulses on a measuring unit and / or on a measuring element of the measuring device, wherein the two laser pulses of the pair are each assigned to different amplified coherent laser beams.

[0043] If the amplified coherent laser beams are pulsed laser beams, in a preferred embodiment the defined time offset corresponds to a repetition rate of the pulsed laser beams.

[0044] It is also possible in principle for a laser source of the device, by means of which coherent laser beams are provided, to be controlled by the measuring device to generate different pairs of laser pulses with a defined time offset.

[0045] Alternatively or additionally, it can be provided that the device for generating different pairs of laser pulses with a defined time offset comprises a shutter device, wherein the shutter device is arranged in particular in a beam path of the amplified coherent laser beams to be coupled into the measuring device and / or of the at least one reference laser beam to be coupled into the measuring device.

[0046] In particular, the shutter device is configured to enable or interrupt the transmission of amplified coherent laser beams and / or the at least one reference laser beam to the respective measuring unit of the measuring device.

[0047] In particular, by appropriately controlling the shutter device using the measuring device, different pairs of laser pulses with a defined time offset can be generated.

[0048] In particular, it can be provided that the shutter device is controlled by the measuring device in such a way that the transmission of amplified coherent laser beams and / or the at least one reference laser beam to the respective measuring unit is enabled only for a period of time required to transmit a specific pair of laser pulses to the associated measuring unit and / or the associated measuring element. This allows, in particular, the use of measuring elements whose measurement bandwidth is lower than the modulation bandwidth of the laser pulses.

[0049] The shutter device can be implemented, for example, mechanically or electro-optically. In particular, the shutter device can be implemented as a photonic integrated circuit.

[0050] In a further variant, it can be provided that in order to form different pairs of laser pulses with a defined time offset, at least one delay element is provided which is designed to form a propagation time difference and / or a path length difference between the two amplified coherent laser beams which are superimposed at the respective measuring unit.

[0051] In a further embodiment, at least one measuring unit is provided, which has at least two and preferably three or more measuring elements. In particular, the measuring device is then configured to supply each of the measuring elements with a pair of a laser pulse of one of the N amplified coherent laser beams and a laser pulse of the other of the N amplified coherent laser beams or of the at least one reference laser beam. It can be provided that each measuring unit of the measuring device has at least two and preferably three or more measuring elements.

[0052] In particular, the pairs supplied to the different measuring elements each have a different offset phase difference.

[0053] In particular, at least two, and preferably three or more, different pairs are provided, whose associated laser pulses and / or associated amplified coherent laser beams each have different, defined offset phase differences. This allows the phase difference between these amplified coherent laser beams to be unambiguously determined by intensity measurements using the sensor element(s), for example, based on a Clarke transformation.

[0054] It can be provided that the phase adjustment device is controlled by means of the measuring device in order to form several pairs whose laser pulses each have a defined and / or different offset phase difference.

[0055] Alternatively or additionally, one or more delay elements may be provided to form multiple pairs with different offset phase differences, wherein, in particular, one or more delay elements may be assigned to each of the measuring elements of the measuring device. A delay element is used, in particular, to generate a path length difference between the two amplified coherent laser beams assigned to the respective laser pulses of a specific pair.

[0056] In particular, it can be provided that the measuring device comprises at least one measuring unit with a measuring element, wherein the measuring device and / or the measuring unit are configured to superimpose two amplified coherent laser beams with an offset phase difference of more than 2*Pi on the measuring element. This can be achieved, for example, by means of one or more delay elements assigned to one of the two amplified coherent laser beams. This makes it possible, in particular, to determine whether amplified coherent laser beams and / or respective laser pulses of the amplified coherent laser beams have a phase difference of more than 2*Pi.

[0057] In particular, it can be provided that the measuring device is configured to control the phase adjustment device in order to control and / or regulate the respective phase difference between the amplified coherent laser beams. For example, a control device is assigned to the measuring device for controlling the phase adjustment device, or the measuring device comprises a control device. The phase adjustment device is controlled in particular on the basis of phase differences between the amplified coherent laser beams measured and / or determined by the measuring device. This allows, for example, the respective phase differences between the amplified coherent laser beams to be controlled by means of the measuring device and, in particular, to be controlled to predetermined target values.

[0058] In particular, a change in the phase difference between the coherent laser beams carried out by means of the phase adjustment device causes a change in the phase difference between the corresponding amplified coherent laser beams.

[0059] In one embodiment, the device comprises a splitting device for splitting an input laser beam into a plurality of coherent laser beams. This allows, for example, a plurality of coherent laser beams to be provided using a single laser source.

[0060] In one embodiment, the device comprises a combination device for combining the amplified coherent laser beams into the at least one combined laser beam. The combination device comprises, for example, at least one microlens array and / or at least one diffractive optical element and / or at least one interferometer optical system and / or at least one polarization-influencing element. For example, the combination device comprises at least one diffractive optical element, wherein the at least one diffractive optical element comprises, for example, a grating structure with a periodic pattern. This makes it possible, for example, to combine the coherent laser beams according to the "filled-aperture" principle.

[0061] The combining device may comprise at least one microlens array for combining the coherent laser beams. This allows, for example, a combination of the coherent laser beams according to the "mixed aperture" principle to be realized.

[0062] It can be provided that the combination device has a frequency conversion stage, or that a frequency conversion stage of the device is assigned to the combination device. In particular, the frequency conversion stage is connected upstream of the combination device.

[0063] It is also possible, in principle, for the amplified coherent laser beams to be combined into the at least one combined laser beam without a combination device. For example, the amplified coherent laser beams are then combined into the at least one combined laser beam by propagation in the far field ("tiled aperture" principle).

[0064] For example, at least one lens element can be provided to image the amplified coherent laser beams into at least one combined laser beam. This allows, for example, a combination of the coherent laser beams to be realized according to the "tiled aperture" principle.

[0065] In particular, it can be provided that the device comprises at least one laser source for providing the coherent laser beams.

[0066] According to the invention, the laser system mentioned above comprises at least one laser source for providing coherent laser beams and a device, as described above, for combining the coherent laser beams. In particular, a single laser source or multiple laser sources can be provided to provide the coherent laser beams. In the case of a single laser source, multiple coherent laser beams are generated by splitting an input laser beam provided by this laser source. In the case of multiple laser sources, at least one coherent laser beam is provided by each of the laser sources, for example.

[0067] According to the invention, in the method for combining coherent laser beams mentioned at the outset, it is provided that a respective phase difference between the coherent laser beams is or is set by means of a phase adjustment device, the coherent laser beams are amplified by means of an amplification device, amplified coherent laser beams being coupled out of the amplification device, and that phase differences between the amplified coherent laser beams are determined by means of a measuring device, wherein in order to determine the phase differences between the amplified coherent laser beams, a phase difference between one of the amplified coherent laser beams and another of the amplified coherent laser beams or between one of the amplified coherent laser beams and at least one reference laser beam is measured.

[0068] In particular, the method according to the invention has one or more further features and / or advantages of the device according to the invention.

[0069] In particular, the method according to the invention is carried out by means of the device according to the invention and / or the device according to the invention is designed to carry out the method according to the invention.

[0070] In particular, it can be provided that the phase adjustment device is controlled by the measuring device and / or by a control device in order to control and / or regulate the respective phase difference between the amplified coherent laser beams. In particular, the terms "at least approximately" or "approximately" generally refer to a deviation of no more than 10%. Unless otherwise stated, the terms "at least approximately" or "approximately" refer in particular to the fact that an actual value and / or distance and / or angle deviates from an ideal value and / or distance and / or angle by no more than 10%.

[0071] The following description of preferred embodiments, taken in conjunction with the drawings, serves to further explain the invention. They show:

[0072] Fig. 1 is a schematic representation of a device for combining several coherent laser beams;

[0073] Fig. 2a shows a combination element designed as a diffractive optical element for combining amplified coherent laser beams into a combined laser beam;

[0074] Fig. 2b shows a combination element designed as a microlens array for combining amplified coherent laser beams into a combined laser beam;

[0075] Fig. 2c a lens element for focusing amplified coherent laser beams;

[0076] Fig. 3 is a schematic representation of an output device for the partial output of amplified coherent laser beams in order to supply them to a measuring device;

[0077] Fig. 4 is a schematic representation of measuring units of the measuring device, wherein the measuring units are used to measure a phase difference between pairs of adjacent amplified coherent laser beams; Fig. 5 is a schematic representation of measuring units of the measuring device, wherein the measuring units are used to measure a phase difference between pairs of the same first and another of the coherent laser beams;

[0078] Fig. 6 is a schematic representation of another configuration of measuring units of the measuring device;

[0079] Fig. 7a is a schematic representation of an embodiment of a measuring unit, wherein the measuring unit has three measuring sections, each with a measuring element;

[0080] Fig. 7b, c, d are schematic representations of laser pulses of the amplified coherent laser beams, each impinging on the different measuring elements of the measuring unit according to Fig. 7a, wherein pairs of laser pulses with different time offsets impinge on the respective measuring elements;

[0081] Fig. 8 is a schematic representation of an intensity curve measured by means of a measuring element as a function of a phase difference between respective laser pulses of two different amplified coherent laser beams.

[0082] Fig. 9a is a schematic representation of an embodiment of a measuring unit having a single measuring element;

[0083] Fig. 9b is a schematic representation of laser pulses of the amplified coherent laser beams, wherein pairs of laser pulses each impinge on the measuring element with a different time offset and wherein different pairs impinge on the measuring element with a time offset;

[0084] Fig. 10 is a schematic representation of another embodiment of a measuring unit having a single measuring element; Fig. 11 is a schematic representation of an embodiment of a measuring unit having a measuring element, wherein delay elements are provided to generate an offset phase difference of more than 2*Pi;

[0085] Fig. 12a shows an example of a temporal progression of set target phase difference values ​​between two amplified coherent laser beams;

[0086] Fig. 12b shows an example of a temporal sequence of measurements carried out by means of a measuring device for measuring actual phase difference values ​​between the amplified coherent laser beams;

[0087] Fig. 12c shows an example of a time course of a deviation between target phase difference values ​​and actual phase difference values; and

[0088] Fig. 12d shows an example of a temporal sequence of an optimization of an assignment rule on the basis of which the target phase difference values ​​are set.

[0089] Identical or functionally equivalent elements are provided with the same reference numerals in all figures.

[0090] An embodiment of a device for combining coherent laser beams is shown schematically in Fig. 1 and designated therein by 100. By means of the device 100, a combination of the coherent laser beams 102 can be carried out (coherent beam combining), whereby one or more combined laser beams 104 are formed.

[0091] In the embodiment according to Fig. 1, it is provided that an input laser beam 108 is provided by means of a laser source 106, and a plurality of coherent laser beams 102 are formed by splitting the input laser beam 108. Alternatively, it is also possible for a plurality of laser sources 106 to be provided to provide the coherent laser beams 102. For example, one or more coherent laser beams 102 are then provided by means of a respective laser source 106.

[0092] A splitting device 110 is provided for splitting the input laser beam 108 into a plurality of coherent laser beams 102. For example, three coherent laser beams 102 are shown in Fig. 1, which are formed by splitting the input laser beam 108 by means of the splitting device 110.

[0093] The input laser beam 108 and / or the coherent laser beams 102 are, for example, pulsed laser beams and in particular ultrashort pulse laser beams.

[0094] The coherent laser beams 102 have, in particular, the same properties, such as the same wavelength and / or the same spectrum.

[0095] A phase adjustment device 112 is provided for adjusting a respective phase difference between the individual coherent laser beams 102. The phase adjustment device 112 comprises, in particular, a plurality of phase adjustment elements 114, wherein a phase of an associated coherent laser beam 102 can be adjusted by means of a specific phase adjustment element 114. For example, a phase adjustment element 114 is assigned to several or all of the coherent laser beams 102.

[0096] In the case of N coherent laser beams 102, the phase adjustment device 112 comprises, for example, N1 or N phase adjustment elements 114.

[0097] For technical details on combining coherent laser beams, please refer to the scientific publications "Coherent combination of ultrafast fiber amplifiers", Hanna, et al., Journal of Physics B: Atomic, Molecular and Optical Physics 49(6) (2016), 062004; "Performance scaling of laser amplifiers via coherent combination of ultrashort pulses", Klenke, Mensch und Buch Verlag; "Coherent beam combining with an ultrafast multicore Yb-doped fiber amplifier", Ramirez, et al., Optics Express 23(5), (2015), 5406-5416; and "Highly scalable femtosecond coherent beam combining demonstrated with 19 fibers", Le Dortz, et al., Optics Letters 42(10), (2017), 1887-1890.

[0098] To amplify the coherent laser beams 102, the device 100 comprises an amplification device 120. In particular, the amplification device 120 comprises a plurality of amplification elements 122, wherein, for example, a amplification element 122 is assigned to each of the coherent laser beams 102.

[0099] In the example shown in Fig. 1, the coherent laser beams 102 are coupled into the amplification device 120 or into the respective amplification elements 122 of the amplification device 120. In particular, before the coherent laser beams 102 are coupled into the amplification device 120, the respective phase differences between the coherent laser beams 102 are adjusted by means of the phase adjustment device 112.

[0100] The coherent laser beams 102, which were amplified by the amplification device 120, are hereinafter referred to as amplified coherent laser beams 124. In the example shown, a number of existing coherent laser beams 102 corresponds to a number of existing amplified coherent laser beams 124.

[0101] For combining the amplified coherent laser beams 124, a combination device 126 is provided in particular, by means of which the combined laser beam 104 is formed by combining the amplified coherent laser beams 124.

[0102] For example, amplified coherent laser beams 124 coupled out of the amplification device 120 are coupled into the combination device 126.

[0103] In one embodiment, the combining device 126 comprises a diffractive optical element 128 for combining the amplified coherent laser beams 124 (Fig. 2a). For focusing the amplified coherent laser beams 124 onto the diffractive optical element 128, a lens element 130, for example, is provided (in Figs. 2a, 2b, and 2c, an envelope 132 of the amplified coherent laser beams 124 incident on the combining device 126 or on the lens element 130 is indicated).

[0104] For example, the diffractive optical element 128 is or includes a grating structure with a periodic pattern.

[0105] For technical details on combining coherent laser beams using diffractive optical elements, please refer to the scientific publications "Coherent combination of ultrashort pulse beams using two diffractive optics", Zhou et al., Opt. Lett. 42, 4422-4425 (2017) and "Diffractive-optics-based beam combination of a phase-locked fiber laser array", Cheung et al., Opt. Lett. 33, 354-356 (2008).

[0106] Alternatively or additionally, it may be provided that the combining device 126 comprises a microlens array 134 for combining the amplified coherent laser beams 124 (Fig. 2b).

[0107] With regard to the technical details on the combination of coherent laser beams by means of one or more microlens arrays, reference is made to WO 2020 / 016336 A1 and to DE 10 2020 201 161 A1 of the same applicant.

[0108] It is also possible in principle for the combination of the amplified coherent laser beams 124 to occur without a combination device 126. For example, the combined laser beam 104 is then formed by superimposing the amplified coherent laser beams 124 in the far field.

[0109] In particular, a lens element 136 can then be provided for focusing the amplified coherent laser beams 124 (Fig. 2c). To measure the respective phase difference A <p zwischen den verstärkten kohärenten Laserstrahlen 124 umfasst die Vorrichtung 100 eine Messeinrichtung 138, welche beispielsweise bezüglich einer Haupt-Propagationsrichtung 140 der kohärenten Laserstrahlen 102 und / oder der verstärkten kohärenten Laserstrahlen 124 nach der Verstärkungseinrichtung 120 angeordnet ist.

[0110] In particular, the measuring device 138 is positioned between the amplifying device 120 and the combining device 126.

[0111] The various amplified coherent laser beams 124 each have a certain phase difference A <p auf (angedeutet in Fig. 3), welche mittels der Messeinrichtung 138 ermittelt werden soll. Unter den Phasendifferenzen A<p sind mittels der Messeinrichtung 138 ermittelte Ist- Phasendifferenzen und / oder Ist-Phasendifferenzwerte zwischen den verstärkten kohärenten Laserstrahlen 124 zu verstehen.

[0112] In order to proportionally feed the amplified coherent laser beams 124 to the measuring device 138, an output coupling device 142 can be provided (Fig. 3). This output coupling device 142 is arranged, in particular, downstream of the amplification device 120 and / or upstream of the combination device 126 with respect to the main propagation direction 140.

[0113] For example, the decoupling device 142 is arranged in a beam path 144 of the amplified coherent laser beams 124. Beam components of the amplified coherent laser beams 124 are decoupled by the decoupling device 142 in order to couple them into the measuring device 138.

[0114] Amplified coherent laser beams 124-ei incident on the outcoupling device 142 are split by the outcoupling device 142 into outcoupled amplified coherent laser beams 124-ak and transmitted amplified coherent laser beams 124-tr.

[0115] The coupled-out amplified coherent laser beams 124-ak are each beam portions of the amplified coherent laser beams 124. The amplified coherent laser beams 124 are thus fed proportionally to the measuring device 138 by means of the coupling-out device 142.

[0116] In particular, a power and / or an intensity of the outcoupled amplified coherent laser beams 124-ak is less than 10% and in particular less than 5% of a power or intensity of the incident amplified coherent laser beams 124-ei.

[0117] The measuring device 138 has an input 146 for coupling the beam components of the amplified coherent laser beams 124 into the measuring device 138. In particular, the respective beam components of the amplified coherent laser beams are coupled separately and / or spatially separated into the measuring device 138.

[0118] The measuring device 138 comprises one or more measuring units 148. For example, in the case of N amplified coherent laser beams 124, the measuring device comprises N or N1 measuring units.

[0119] In the example shown in Figs. 3 and 4, four amplified coherent laser beams 124 are provided, the beam components of which are each coupled into the measuring device 138. These four amplified coherent laser beams, for example, are designated 124-1, 124-2, 124-3, and 124-4 below.

[0120] By means of the measuring units 148, phase differences A <p zwischen den unterschiedlichen verstärkten kohärenten Laserstrahlen 124 gemessen, wobei die Phasendifferenzen A<p jeweils für unterschiedliche 2er- Paare und / oder 2er-Kombinationen der verstärkten kohärenten Laserstrahlen 124 ermittelt werden.

[0121] It is also possible in principle that by means of the measuring device 138 and / or by means of the measuring units 148 of the measuring device 138 phase differences A <p jeweils paarweise zwischen einem der verstärkten kohärenten Laserstrahlen 124 und einem Referenzlaserstrahl 149 gemessen werden. Beispielsweise kann der Referenzlaserstrahl 149 ein aus der Laserquelle 106 ausgekoppelter Laserstrahl und / oder ein Strahlanteil des Eingangslaserstrahls 108 sein. Es ist auch möglich, dass der Referenzlaserstrahl 149 einer der aus der Aufteilungseinrichtung 110 ausgekoppelten kohärenten Laserstrahlen 102 ist (beide Varianten sind in Fig. 1 durch die gepunktete Linie angedeutet).

[0122] It can be provided that a phase adjustment element 114 and / or an amplification element 122 are assigned to the reference laser beam 149.

[0123] In one variant, the reference laser beam 149 is coupled into the measuring device 138 by means of the coupling-out device 142, wherein in particular a proportion of at least 90% and / or at least approximately 100% of the reference laser beam 149 is coupled into the measuring device 138 (indicated in Fig. 1).

[0124] Depending on the embodiment, the amplified coherent laser beam designated 124-1 in Fig. 4 may, for example, correspond to the reference beam 149.

[0125] It is also possible in principle for the reference laser beam 149 to be coupled into the measuring device 138 by means of a separate beam path, which in particular does not lead through the coupling-out device 142 (not shown).

[0126] In the embodiment according to Fig. 4, a phase difference A <p zwischen den verstärkten kohärenten Laserstrahlen 124-1 und 124-2, 124-2 und 124-3 sowie 124-3 und 124-4 gemessen, wobei die Phasendifferenz A<p den unterschiedlichen Paaren aus zwei verstärkten kohärenten Laserstrahlen 124 jeweils mittels einer unterschiedlichen Messeinheit 148 gemessen wird.

[0127] In the example shown in Fig. 4, the phase difference A <p für drei unterschiedliche Kombinationen bestehend aus jeweils zwei der verstärkten kohärenten Laserstrahlen 124-1, 124-2, 124-3, 124-4 gemessen. Folglich wird jeweils eine Phasendifferenz A<p zwischen einem ersten der verstärkten kohärenten Laserstrahlen 124-1, 124-2, 124-3, 124-4 und genau einem weiteren der verstärkten kohärenten Laserstrahlen 124-1, 124-2, 124-3, 124-4 gemessen, wobei der erste und der genau eine weitere der verstärkten kohärenten Laserstrahlen 124-1, 124-2, 124-3, 124-4 jeweils bei allen Messungen unterschiedlich ist.

[0128] Fig. 5 shows a further embodiment of a measuring device 138. In this example, a phase difference A <p zwischen den verstärkten kohärenten Laserstrahlen 124-1 und 124-2 bzw. 124-1 und 124-3 bzw. 124-1 und 124-4 gemessen.

[0129] In the example shown in Fig. 5, the phase difference A <p für drei unterschiedliche Kombinationen bestehend aus jeweils zwei der verstärkten kohärenten Laserstrahlen 124-1, 124-2, 124-3, 124-4 gemessen. Folglich wird jeweils eine Phasendifferenz A<p zwischen einem ersten der verstärkten kohärenten Laserstrahlen 124-1, 124-2, 124-3, 124-4 und genau einem weiteren der verstärkten kohärenten Laserstrahlen 124-1, 124-2, 124-3, 124-4 gemessen, wobei der erste der verstärkten kohärenten Laserstrahlen 124- 1, 124-2, 124-3, 124-4 jeweils bei allen Messungen unterschiedlich ist und der genau eine weitere bei allen Messungen derselbe ist (bei dem gezeigten Beispiel nämlich der verstärkte kohärente Laserstrahl 124-1).

[0130] In a variant of the example shown in Fig. 5, the amplified coherent laser beam 124-1 may correspond to the reference beam 149.

[0131] In the example shown in Fig. 6, six amplified coherent laser beams 124-1, 124-2, 124-3, 124-4, 124-5, and 124-6 are present. In this example, the phase difference A <p für fünf unterschiedliche Kombinationen bestehend aus jeweils zwei der verstärkten kohärenten Laserstrahlen gemessen. Es wird jeweils eine Phasendifferenz A<p zwischen einem ersten der verstärkten kohärenten Laserstrahlen und genau einem weiteren der verstärkten kohärenten Laserstrahlen gemessen, wobei der erste der verstärkten kohärenten Laserstrahlen bei allen Messungen unterschiedlich und der genau eine weitere der verstärkten kohärenten Laserstrahlen bei drei der Messungen der verstärkte kohärente Laserstrahl 124-3 (Messungen zwischen den verstärkten kohärenten Laserstrahlen 124-1 und 124-3, 124-2 und 124-3, 124-4,124-3) ist und bei zwei der Messungen der verstärkte kohärente Laserstrahl 124-4 ist (Messungen zwischen den verstärkten kohärenten Laserstrahlen 124-6 und 124-4, 124-5 und 124-6).

[0132] Beam guidance within the measuring device 138 can, for example, be free-jet based and / or fiber-based and / or waveguide-based.

[0133] In a particularly preferred embodiment, the measuring device 138 is embodied, at least in part, as a photonic integrated circuit (PIC). In this case, comparable to integrated circuits, optical components and / or beam guidance components are arranged on a substrate, such as a silicon substrate, silicon nitride substrate, and / or a lithium niobate-on-insulator substrate.

[0134] Regarding the realization and properties of optical components and / or beam guidance components as PIC, reference is made to the scientific publication "Direct and Sensitive Phase Readout for Integrated Waveguide Sensors", by R. Halir et al., IEEE Photonics Journal, Volume 5, Number 4, August 2013, DOI: 10.1109 / JPHOT.2013.2276747.

[0135] An embodiment of the measuring unit 148 is shown in Fig. 7. The measuring unit 148 comprises one or more measuring elements 150. In the example shown, three measuring elements 150a, 150b, 150c are provided.

[0136] The measuring element 150 is designed to measure the intensity of a laser beam incident thereon or of a superposition of laser beams incident thereon in a time-resolved manner. For example, the measuring element 150 is or includes a photodiode.

[0137] The measuring unit 148 comprises a first input 152a for coupling in a first amplified coherent laser beam 124, for example, the amplified coherent laser beam 124-1, and a second input 152b for coupling in a second amplified coherent laser beam 124, for example, the amplified coherent laser beam 124-2. The two amplified coherent laser beams 124-1 and 124-2 coupled in via the first input 152a and the second input 152b are superimposed and, in particular, collinearly superimposed at the measuring element 150.

[0138] To superimpose the two amplified coherent laser beams 124-1 and 124-2, a superimposition element 154 is assigned to the measuring element 150. For example, the superimposition element 154 is designed as a Y-coupler, and in particular as a fiber-based Y-coupler. For example, the superimposition element 154 can be designed as a multimode interference coupler (MMI coupler).

[0139] The two amplified coherent laser beams 124-1 and 124-2 are spatially distributed among the various measuring elements 150 of the measuring unit 148. In the example shown in Fig. 7, the amplified coherent laser beams 124-1 and 124-2 are distributed among the three measuring elements 150a, 150b, and 150c. Different beam paths, for example, are provided to distribute the two amplified coherent laser beams 124-1 and 124-2 among the various measuring elements 150.

[0140] The measuring device 138 and / or the measuring unit 148 are designed such that at least three different measured values ​​are determined by means of each measuring unit 148 for the amplified coherent laser beams 124 coupled into it, wherein the different measured values ​​are each assigned a different offset phase difference A <p off is assigned.

[0141] If the amplified coherent laser beams 124 are pulsed laser beams, the amplified coherent laser beams 124 each have laser pulses 156. The offset phase difference A <p off is then accompanied by a time offset with which the respective laser pulses 156 of the two amplified coherent laser beams 124 hit the measuring element 150 (Fig. 7b, 7c and 7d).

[0142] In the example shown in Fig. 7a, a measured value for a pair 158 of a first laser pulse 156 and a further laser pulse 156 is recorded at one of the measuring elements 150, wherein in particular the respective offset phase differences A <p offat the various measuring elements 150 of the measuring unit 148 are different. The first laser pulse 156 and the further laser pulse 156 are assigned to different ones of the two coherent amplified coherent laser beams 124, which are coupled into the measuring unit 148 and / or into the measuring element 150.

[0143] In particular, the pair 158 is to be understood as a spatial superposition of the first and the further laser pulse 156 on the measuring element 150, wherein these laser pulses 156 have a defined offset phase difference A <p off on the measuring element 150.

[0144] In Figs. 7b, 7c, and 7d, the laser pulses associated with the amplified coherent laser beam 124-1 are designated 156-1, and the laser pulses associated with the amplified coherent laser beam 124-2 are designated 156-2. Fig. 7b schematically shows the temporal offset of the laser pulses 156-1 and 156-2 impinging on the measuring element 150a, Fig. 7c shows the laser pulses 156-1 and 156-2 impinging on the measuring element 150b, and Fig. 7d shows the laser pulses 156-1 and 156-2 impinging on the measuring element 150c.

[0145] To form different offset phase differences A <p off Delay elements 160 can be provided between the laser pulses 156-1 and 156-2 at the various measuring elements 150, wherein one or more delay elements 160 can be assigned to one or more of the measuring elements 150.

[0146] For example, the delay element 160 is designed to generate a path length difference from which, for example, a time offset and / or an offset phase difference A <p off between the laser pulses 156 of the pair 158.

[0147] In the example according to Fig. 7a, a respective delay element 160 is used, for example, to form an offset phase difference A <p off of 120°. In the example shown, no delay element 160 is assigned to the amplified coherent laser beam 124-2 coupled into the measuring elements 150a, 150b, and 150c.

[0148] Furthermore, no delay element 160 is assigned to the measuring element 150a and / or the amplified coherent laser beam 124-1 coupled into the measuring element 150a. This results in, for example, an offset phase difference A <p off of 0° between the two laser pulses 156-1 and 156-2.

[0149] A single delay element 160 is assigned to the measuring element 150b and / or the amplified coherent laser beam 124-1 coupled into the measuring element 150b. This results in, for example, an offset phase difference A <p off of 120° between the two laser pulses 156-1 and 156-2.

[0150] For example, two delay elements 160 are assigned to the measuring element 150c and / or the amplified coherent laser beam 124-1 coupled into the measuring element 150c. This results in, for example, an offset phase difference A <p off of 240° between the two laser pulses 156-1 and 156-2.

[0151] Due to the majority of measurements carried out by the measuring unit 148, 124 measured values ​​are obtained for the two amplified coherent laser beams assigned to the measuring unit 148 at different offset phase differences A <p offBased on these measured values, the actual phase difference A <p zwischen diesen beiden verstärkten kohärenten Laserstrahlen 124 ermitteln.

[0152] By means of the measuring elements 150 of the measuring unit 148, intensities I of a superposition of the laser pulses 156-1, 156-2 belonging to the pair 158 are measured, wherein the measured intensity I depends on the offset phase difference A <p off (Fig. 8). In particular, a time-averaged intensity I of the laser pulses 156 of the pair 158 impinging on the measuring element 150 is measured by means of a respective measuring element 150. Fig. 8 shows an example of an intensity I measured at a measuring element 150 as a function of the phase difference A <p gezeigt. Bei dem in Fig. 8 gezeigten Beispiel sind drei unterschiedliche Messwerte Mi, M2, M3 angedeutet, wobei beispielsweise der Messwert Mi mit dem Messelement 150a und Fig. 7b (A<p off=0°), the measured value M2 with the measuring element 150b and Fig. 7c (A <p off =120°) and the measured value M3 with the measuring element 150c and Fig. 7d (A <p off =240°) corresponds.

[0153] In the embodiment according to Fig. 7a, measured values ​​for different offset phase differences A <p off by means of various measuring elements 150, wherein, for example, a measuring element 150 is assigned to a measured value for a specific offset phase difference A <p off In particular, in the example according to Fig. 7a, a temporally parallel measurement of pairs 158 of superimposed laser pulses 156 with different offset phase differences A <p off .

[0154] Alternatively, in the embodiment of a measuring unit 148' shown in Fig. 9a, it is provided to carry out measurements of pairs 158 of two laser pulses 156 for different offset phase differences A <poff to be carried out at a different time. The embodiment of the measuring unit 148' shown in Fig. 9a differs from the embodiment described above and shown in Fig. 7a in that a single measuring element 150 is provided. Otherwise, the measuring unit 148' is constructed similarly to the measuring unit 148, so that reference is made to its description in this regard.

[0155] In this embodiment, it is provided that the pairs 158 with different offset phase differences A <p off are guided to the measuring element 150 with a time offset, wherein the respective pairs 158, for example, hit the measuring element 150 with a defined time offset Δt (Fig. 9b).

[0156] Different measured values ​​Mi, M2, M3 are thereby recorded sequentially by means of the measuring element 150. In this embodiment, the measuring device 138 is designed to provide the pairs 158 of two laser pulses 156 with a defined time offset Δt and respectively defined offset phase differences A <p off furnished.

[0157] If the amplified coherent laser beams 124 are pulsed laser beams, in a preferred embodiment the defined time offset Δt corresponds at least approximately to a repetition rate of the pulsed laser beams.

[0158] For example, the repetition rate is in the range of 1 MHz to 1 GHz.

[0159] In particular, it can be provided that the phase adjustment device 112 is controlled by means of the measuring device 138 in order to generate pairs 158 with a defined offset phase difference A <p offIn particular, the measuring device 138 is configured to control the phase adjustment device 112 and / or is connected to the phase adjustment device 112 in a signal-effective manner.

[0160] It is also fundamentally possible for the measuring device 138 to control the laser source 106 in order to provide pairs 158 with a defined time offset Δt. For this purpose, the measuring device 138 is, for example, connected to the laser source 106 and / or to a control device of the laser source 106 in a signal-effective manner.

[0161] Alternatively or additionally, in order to generate the pairs 158 with a defined time offset Δt, a shutter device 162 which can be controlled by means of the measuring device 138 and which is arranged in the beam path of the coherent laser beams 102 and / or the amplified coherent laser beams 124 can be provided (Fig. 3).

[0162] The shutter device 162 is configured to interrupt or enable the transmission of amplified coherent laser beams 124 to the respective measuring units 148 of the measuring device 138. For example, the shutter device 162 comprises a plurality of shutter elements 164, each shutter element being assigned to one of the amplified coherent laser beams 124. By appropriately controlling the shutter device 162 with the measuring device 138, laser pulses 156 and / or pairs 158 of laser pulses 156 of the respective amplified coherent laser beams 124 can be supplied to a specific measuring element 150 with a defined time offset Δt. This can be provided in particular when the amplified coherent laser beams are continuous-wave laser beams.

[0163] One or more of the shutter elements 164 can, for example, be arranged in the respective beam path of the amplified coherent laser beams 124 coupled into the measuring device 138. It is also possible in principle for shutter elements 164 to be assigned to a measuring unit 148 and / or a measuring element 150 or to be part of a measuring unit 148 and / or a measuring element 150.

[0164] It is also possible in principle to apply the pairs 158 of laser pulses 156 directed to the measuring element 150 with a defined time offset Δt and a defined offset phase difference Δt <p off by splitting the amplified coherent laser beams 124-1, 124-2 coupled into the measuring unit 148' into different beam paths 166 (Fig. 10). In particular, the different beam paths are each configured to form a pair 158 with a defined offset phase difference A <p offand to supply it to the measuring element 150 with a specific time offset Δt to a next or previous pair 158. To form the defined time offset Δt and the defined offset phase difference A <p off Delay elements 160 may be provided, which are arranged in the respective beam paths 166.

[0165] Preferably, one or more delay elements 160 and / or one or more beam paths 166 may be implemented as PIC.

[0166] In the example shown in Fig. 10, three different beam paths 166 are provided to provide the measuring element 150 with three pairs 158 with a defined time offset Δt and a defined offset phase difference Δt <p off A pair 158 is provided by each of the beam paths.

[0167] It can be provided that the measuring device 138 controls the shutter device 162 to perform a measurement in order to supply pairs 158 of laser pulses 156 to the measuring units 148 and / or the measuring elements 150. In particular, the shutter device 162 is controlled such that the shutter elements 164 are only enabled for a period of time required to allow a specific pair 158 of laser pulses 156 to pass to the associated measuring unit 148 and / or the associated measuring element 150.

[0168] In particular, it may be provided that the measuring device 138 is configured to supply the amplified coherent laser beams 124 to the respective measuring units 148 and / or measuring elements 150 with at least approximately the same intensity. For this purpose, it may be provided that the measuring device 138 comprises amplification elements.

[0169] In one embodiment, it can be provided that the measuring device 138 comprises at least one measuring unit 148" with a measuring element 150, wherein it is provided that the two coupled amplified coherent laser beams 124-1, 124-2 and / or the coupled pair 158 of laser pulses 156 of these amplified coherent laser beams have an offset phase difference A <p off of more than 2*Pi (Fig. 11). This can be realized, for example, by a plurality of delay elements 160, to which one of the two amplified coherent laser beams 124-1, 124-2 coupled into the measuring unit 148" is assigned.

[0170] During operation of the device 100, it is provided that the phase adjustment device 112 is controlled in order to adjust the respective phase difference between the amplified coherent laser beams 124 to predetermined target phase difference values ​​A <p so". In the example shown, the phase adjustment device 112 can be used to adjust the respective phase difference between the coherent laser beams 102 coupled into the amplification device 120, which causes a change and / or adjustment of the respective phase difference between the associated amplified coherent laser beams 124.

[0171] The device comprises a control device 168, which controls the phase adjustment device 110 with specific control values ​​based on an assignment rule. The assignment rule contains an assignment of the control values ​​to desired phase difference values ​​A <p so " between the respective amplified coherent laser beams. For example, the assignment rule is or includes an assignment table.

[0172] For example, a starting version of the assignment rule is determined by calibration measurements. During these calibration measurements, for example, the phase adjustment device 112 is controlled by the control device 168 with specific control values, and the resulting actual phase difference values ​​A are determined for these control values ​​by means of the measuring device 138. <p gemessen. Es lassen sich dadurch Zusammenhänge zwischen den Ansteuerwerten und den resultierenden Phasendifferenzwerten A<p ermitteln, um die Zuordnungsvorschrift zu definieren.

[0173] In particular, a memory device 170 may be provided which is comprised by the control device 168 or which is assigned to the control device 168, wherein the assignment rule is stored in the memory device 170.

[0174] During operation of the device 100, deviations may occur between the target phase difference values ​​A set on the basis of the assignment rule <p so " and the actual phase difference values ​​A actually obtained by means of the measuring device 138 <p der verstärkten kohärenten Laserstrahlen 124 kommen.

[0175] It is intended that the assignment rule is optimized during operation of the device 100 in order to minimize the deviation between the desired phase difference values ​​A <p so " and the actual phase difference values ​​A <p zu minimieren. Zur Durchführung der Optimierung ist eine der Steuerungseinrichtung 168 zugeordnete Optimierungseinheit 172 vorgesehen.

[0176] The optimization unit 172 at least partially adapts and / or changes the assignment rule in order to reduce the deviation between the target phase difference values ​​A <p so" and the actual phase difference values ​​A <p zu minimieren, wobei zur Minimierung insbesondere ein Vergleich zwischen den Soll-Phasendifferenzwerten A<p so " and the actual phase difference values ​​A <p vorgenommen wird.

[0177] For example, by means of the optimization unit 172, the allocation rule stored for controlling the phase adjustment device 112 by means of the control device 168 is updated at certain time intervals, ie replaced by a new allocation rule which is adapted as described above.

[0178] The control device 168, the measuring device 138, the storage device 170 and the optimization unit are each connected to one another in a signal-effective manner (indicated by the dashed line in Fig. 1).

[0179] The phase adjustment device 112 is configured to adjust the respective phase difference between the coherent laser beams 102 and / or the amplified coherent laser beams 124 with a phase adjustment frequency f Einstel1 to specified target phase difference values ​​A <p so " (in Fig. 12a, for example, a time course of set target phase difference values ​​A <p so " between two of the amplified coherent laser beams 124). Under this phase adjustment frequency f Einstel1 is a maximum frequency or a smallest time interval At Einstell = i / f Einste " to understand with which the respective phase difference is or is changed. The phase adjustment frequency f Einstel1 is also called the modulation frequency of the phase adjustment device.

[0180] In particular, the phase adjustment frequency f Einstel1 in the range from 1 MHz to 50 MHz.

[0181] The measuring device 138 is set up to measure the respective phase difference A <p (Ist-Phasendifferenz) zwischen den verstärkten kohärenten Laserstrahlen 124 mit einer Messgenauigkeitsfrequenz f Mess9en (Fig. 12b). This includes a maximum frequency or a minimum time period At Mess9en =l / f Mess9en to be understood with which a phase difference can be resolved in time by the measuring device 138. The measurement accuracy frequency f Mess9en is also called measurement bandwidth. In particular, the measurement accuracy frequency f Mess9en greater than or equal to the phase adjustment frequency f Einste ".

[0182] The measuring device 138 described above enables, in particular, measurements of the respective phase difference A <p mit einer Messgenauigkeitsfrequenz f Mess9en in the range from 1 MHz to 50 MHz.

[0183] Furthermore, the measuring device 138 is configured to measure the respective phase difference A <p mit einer Messabstandsfrequenz f Messab (Fig. 12b). This is a frequency or a time interval At Messab =l / f Messab to understand with which the respective phase difference between the amplified coherent laser beams 124 is determined or can be determined by the measuring device 138.

[0184] In particular, the measuring distance frequency f Messab in the range of 0.5 kHz to 5 kHz.

[0185] The optimization unit 172 is configured to apply the allocation rule with an optimization frequency f° pti This is a frequency or a time interval At Opti =l / f° pti to understand with which the stored assignment rule is adapted and / or updated by the optimization unit 172 in order to reduce the deviation between the target phase difference values ​​A <pso " and the actual phase difference values ​​A <p zu minimieren (Fig. 12c).

[0186] In particular, the optimization frequency is in the range of 0.5 kHz to 5 kHz.

[0187] The optimization of the assignment rule with the optimization frequency f° pti is shown schematically in Fig. 12d. In the time interval 0 <t<At Opti The control of the phase adjustment device 112 is carried out by the control device 168 on the basis of a first version 173 of the assignment rule. At time t = At Opti the assignment rule is replaced by an optimized version 173', whereby at this point the deviation between A <p so" and A <p verringert wird (vgl. Fig. 12c). Es kann vorgesehen sein, dass die Vorrichtung 100 mindestens eine Zusatz- Messeinrichtung 174 aufweist, welche vorzugsweise bezüglich der Haupt- Propagationsrichtung 140 nach der Messeinrichtung 138 und / oder nach der Auskopplungseinrichtung 142 angeordnet ist. Diese Zusatz-Messeinrichtung 174 ist zur Ermittlung von Phasendifferenzen A<p (Ist-Phasendifferenzen) zwischen den verstärkten kohärenten Laserstrahlen 124 ausgebildet. Weiter ist die Zusatz- Messeinrichtung 174 zur Übermittlung der ermittelten Phasendifferenzen A<p an die Steuerungseinrichtung 168 signalwirksam mit dieser verbunden.

[0188] The additional measuring device 174 can, for example, be arranged in an area of ​​the combination device 126 and / or in an area of ​​a workpiece (not shown) to be machined by means of the at least one combined laser beam 104.

[0189] Using the additional measuring device 174, further actual phase difference values ​​A <p ermitteln, welche bei der Optimierung der Zuordnungsvorschrift berücksichtigt werden können. Diese Ist- Phasendifferenzwerte A<p werden beispielsweise von der Optimierungseinrichtung 172 zusätzlich zu den von der Messeinrichtung 138 ermittelten Ist- Phasendifferenzwerten A<p zur Optimierung der Zuordnungsvorschrift herangezogen.

[0190] The measuring distance frequency f Messab and / or the measurement accuracy frequency f Mess9en of the additional measuring device 174 may correspond to those of the measuring device 138 or may differ from those of the measuring device 138. In particular, the measurement accuracy frequency f Mess9en the additional measuring device 174 must be lower than that of the measuring device 138.

[0191] It can be provided that the device 100 comprises one or more sensor elements 176, which are configured to measure at least one parameter which represents the respective phase difference A <p zwischen den verstärkten kohärenten Laserstrahlen 124 beeinflusst. Beispielsweise können Sensorelemente 176 jeweils der Phaseneinstelleinrichtung 112 und / oder der Verstärkungseinrichtung 120 zugeordnet sein.

[0192] The sensor elements 176 can, for example, be configured to measure temperature.

[0193] The sensor elements 176 are signal-connected to the control device 168 and / or to the optimization unit 172 for transmitting the measured values ​​acquired by them. The optimization unit 172 takes the measured values ​​acquired by the sensor elements 176 into account when optimizing the assignment rule.

[0194] The device 100 according to the invention functions as follows:

[0195] The input laser beam 108 is provided by the laser source 106 and coupled into the splitting device 110. By splitting the input laser beam 108 by the splitting device 110, a plurality of coherent laser beams 102 are formed. The coherent laser beams 102 are amplified by the amplification device 120 and output as amplified coherent laser beams 124. By combining the amplified coherent laser beams 124, one or more combined laser beams 104 are subsequently formed, wherein the combination is carried out, for example, by the combination device 126.

[0196] To form the combined laser beams 104 with the desired properties, it is necessary to determine the respective phase differences A <p der verstärkten kohärenten Laserstrahlen 124 aufeinander abzustimmen und diese zu steuern und / oder zu regeln.

[0197] To determine the respective phase differences A <p der verstärkten kohärenten Laserstrahlen 124 einzustellen, steuert die Phaseneinstelleinrichtung 168 die Phaseneinstelleinrichtung 110 mit Ansteuerwerten gemäß der Zuordnungsvorschrift an. Es werden dadurch die jeweiligen Phasendifferenzen zwischen den kohärenten Laserstrahlen 102 vor deren Einkopplung in die Verstärkungseinrichtung 120 eingestellt, was wiederum eine Einstellung der jeweiligen Phasendifferenzen A<p der verstärkten kohärenten Laserstrahlen 124 bewirkt.

[0198] The actual phase differences A <p der verstärkten kohärenten Laserstrahlen 124 werden mittels der Messeinrichtung 138 gemessen und an die Steuerungseinrichtung 168 und / oder die Optimierungseinheit 172 übermittelt.

[0199] The optimization unit compares the set target phase difference values ​​with the actually measured phase difference values ​​A <p zwischen den verstärkten kohärenten Laserstrahlen 124 und berechnet hierauf eine aktualisierte Zuordnungsvorschrift, sodass eine Abweichung zwischen den Soll- Phasendifferenzwerten und den Ist-Phasendifferenzwerten A<p minimiert wird.

[0200] The assignment rule can be updated, for example, analogously to the calibration and linearization of nonlinear sensor curves based on reference measurements. Corresponding methods can be adapted so that the calibration process is continuously improved based on individual measured values ​​and, optionally, additional sensor information is taken into account. Such methods can be found, for example, in the publications "Lookup Table Optimization for Sensor Linearization in Small Embedded Systems," L.E. Bengtsson, Journal of Sensor Technology, Vol. 2 No. 4, 2012, pp. 177-184, "A Linearization and Compensation Method for Integrated Sensors," P. Hille, R. Hohler and H. Strack, Sensors and Actuators A, Vol. 44, No. 2, 1994, pp. 95-102, and "Linearization of Analog-to-Digital Converters," A.C. Dent and C.F.N. Cowan, IEEE Transactions on Circuits and Systems, Vol. 37, No. 4. 6, 1990, pp.729-737, which is referred to in connection with the update of the allocation rule.

[0201] It may be provided that, in order to optimize the assignment rule, the measured values ​​determined by means of the additional measuring device 174 and / or the sensor elements 176 are additionally used. List of reference symbols

[0202] I Intensity

[0203] Mi - M3 measured value

[0204] A <p Phasendifferenz / Ist-Phasendifferenzwert

[0205] A <p so " Target phase difference value

[0206] A <p off Offset phase difference

[0207] At Time offset fEinsteii Phase adjustment frequency fMessab Measuring distance frequency fMessgen Measuring accuracy frequency f° pti Optimization frequency

[0208] 100 device

[0209] 102 coherent laser beam

[0210] 104 combined laser beam

[0211] 106 Laser source

[0212] 108 input laser beam

[0213] 110 Distribution device

[0214] 112 Phase adjustment device

[0215] 114 Phase adjustment element

[0216] 120 amplification device

[0217] 122 Reinforcing element

[0218] 124 amplified coherent laser beam

[0219] 124-ei incident amplified coherent laser beam

[0220] 124-tr transmitted amplified coherent laser beam

[0221] 124-ak coupled amplified coherent laser beam

[0222] 124-1 amplified coherent laser beam

[0223] 124-2 amplified coherent laser beam

[0224] 124-3 amplified coherent laser beam

[0225] 124-4 amplified coherent laser beam

[0226] 126 Combination device

[0227] 128 diffractive optical element

[0228] 130 lens element

[0229] 132 envelopes

[0230] 134 microlens array lens element

[0231] measuring device

[0232] Main propagation direction

[0233] Decoupling device

[0234] Beam path

[0235] Entrance

[0236] Unit of measurement ' Unit of measurement

[0237] Reference laser beam

[0238] Measuring element a Measuring element b Measuring element c Measuring element a first input b second input

[0239] Overlay element

[0240] Laser pulse -1 Laser pulse -2 Laser pulse

[0241] Pair of two laser pulses

[0242] Delay element

[0243] Shutter device

[0244] Shutter element

[0245] Beam path

[0246] Control device

[0247] Storage device

[0248] Optimization unit first version of the assignment rule ' optimized version of the assignment rule Additional measuring device

[0249] Sensor element

Claims

Claims: Device for combining coherent laser beams (102) to form at least one combined laser beam (104), comprising a phase adjustment device (112) for adjusting a respective phase difference between the coherent laser beams (102), an amplification device (120) for amplifying the coherent laser beams (102), wherein amplified coherent laser beams (124) are coupled out of the amplification device (120), and a measuring device (138) for determining phase differences (A <p) zwischen den verstärkten kohärenten Laserstrahlen (124), wobei die Messeinrichtung (138) eingerichtet ist,to determine the phase differences (A <p) zwischen den verstärkten kohärenten Laserstrahlen (124) jeweils eine Phasendifferenz (A<p) zwischen einem der verstärkten kohärenten Laserstrahlen (124) und einem weiteren der verstärkten kohärenten Laserstrahlen (124) oder zwischen einem der verstärkten kohärenten Laserstrahlen (124) und mindestens einem Referenzlaserstrahl (149) zu messen. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, dass die Messeinrichtung (138) eingerichtet ist, um jeweils Phasendifferenzen (A<p) zwischen Kombinationen aus zwei unterschiedlichen der verstärkten kohärenten Laserstrahlen (124) zu messen oder um jeweils Phasendifferenzen (A<p) zwischen unterschiedlichen Kombinationen aus jeweils einem der verstärkten kohärenten Laserstrahlen (124) und dem mindestens einen Referenzlaserstrahl (149) zu messen. Vorrichtung nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet,that the measuring device (138) is implemented at least partially as a photonic integrated circuit. Device according to one of the preceding claims, characterized in that N coherent laser beams (102) and / or N amplified coherent laser beams (124) are provided, and that the, Measuring device (138) is set up to measure each phase difference (A <p) für N-l unterschiedliche Kombinationen aus jeweils zwei der N verstärkten kohärenten Laserstrahlen (124) zu messen oder um jeweils eine Phasendifferenz für N unterschiedliche Kombinationen aus jeweils einem der N verstärkten kohärenten Laserstrahlen (124) und dem mindestens einen Referenzlaserstrahl (149) zu messen. Vorrichtung nach Anspruch 4, wobei jeweils eine Phasendifferenz (A<p) zwischen einem ersten der verstärkten kohärenten Laserstrahlen (124) und genau einem weiteren der verstärkten kohärenten Laserstrahlen (124) gemessen wird, wobei der erste der verstärkten kohärenten Laserstrahlen (124) bei allen Messungen unterschiedlich ist, und wobei der genau eine weitere der verstärkten kohärenten Laserstrahlen (124) bei allen Messungen unterschiedlich ist oder wobei der genau eine weitere der verstärkten kohärenten Laserstrahlen (124) bei einer Teilmenge der Messungen oder bei allen Messungen derselbe ist.Device according to one of the preceding claims, characterized by a coupling device (142) for the partial coupling of the amplified coherent laser beams (124), wherein the partially coupled amplified coherent laser beams (124-ak) are supplied to the measuring device (138) in order to determine a respective phase difference (A <p) zwischen den verstärkten kohärenten Laserstrahlen (124) zu messen.Device according to one of the preceding claims, characterized in that the measuring device (138) is used to measure the respective phase difference (A) <p) zwischen den verstärkten kohärenten Laserstrahlen (124) jeweils ein Anteil eines der verstärkten kohärenten Laserstrahlen (124) mit einem Anteil eines weiteren der verstärkten kohärenten Laserstrahlen (124) räumlich überlagert wird und insbesondere räumlich kollinear überlagert wird oder jeweils ein Anteil eines der verstärkten kohärenten Laserstrahlen (124) mit dem mindestens einen Referenzlaserstrahl (149) räumlich überlagert wird und insbesondere kollinear räumlich überlagert wird. Device according to one of the preceding claims, characterized in that N coherent laser beams (102) and / or N amplified coherent laser beams (124) are provided and that the measuring device (138) has at least Nl measuring units (148; 148') which are configured to each measure a phase difference (A <p) zwischen einem der N verstärkten kohärenten Laserstrahlen (124) und einem weiteren der N verstärkten kohärenten Laserstrahlen (124) zu messen, oder dass die Messeinrichtung (138) mindestens N Messeinheiten (148; 148') aufweist, welche eingerichtet sind, um jeweils eine Phasendifferenz (A<p) zwischen einem der N verstärkten kohärenten Laserstrahlen (124) und dem mindestens einen Referenzlaserstrahl (149) zu messen.Device according to claim 8, characterized in that at least one measuring unit (148; 148') is provided, which has a single measuring element (150), wherein one of the N amplified coherent laser beams (124) is spatially superimposed on the measuring element (150) with another of the N amplified coherent laser beams (124) or with the at least one reference laser beam (149), and that the measuring device (138) is configured to supply the measuring element (150) and / or the measuring unit (148; 148') with several pairs (158) of a laser pulse (156-1) of one of the N amplified coherent laser beams (124) and a laser pulse (156-2) of the other of the N amplified coherent laser beams (124) or a laser pulse (156) of the reference laser beam (149), wherein the pairs (158) are supplied to the measuring element (150) and / or supplied to the measuring unit (148, 148') with a defined time offset (At).Device according to claim 8 or 9, characterized in that at least one measuring unit (148; 148') is provided which has at least two and preferably three or more measuring elements (150), and in particular that the measuring device (138) is configured to provide the measuring elements (150) with each pair (158) consisting of a laser pulse (156-1) of one of the N amplified coherent laser beams (124) and a laser pulse (156-2) of the further N amplified coherent laser beams (124) or a laser pulse (156) of the at least one. to supply reference laser beam (149). Device according to claim 9 or 10, characterized in that at least two and preferably three or more different pairs (158) are provided, whose associated laser pulses (156) and / or associated amplified coherent laser beams (124) each have different defined offset phase differences (A <p off). A device according to one of the preceding claims, characterized in that the measuring device (138) is configured to control the phase adjustment device (112) in order to control and / or regulate the respective phase difference between the amplified coherent laser beams. A device according to one of the preceding claims, characterized by a splitting device (110) for splitting an input laser beam (108) into several coherent laser beams (102). A device according to one of the preceding claims, characterized by a combination device (126) for combining the amplified coherent laser beams (124) to form the at least one combined laser beam (104), and in particular characterized in that the combination device (126) comprises at least one microlens array (134) and / or at least one diffractive optical element (128).Laser system comprising at least one laser source (106) for providing coherent laser beams (102) and a device (100) for combining the coherent laser beams (102) according to one of the preceding claims. Method for combining coherent laser beams (102) to form at least one combined laser beam (104) in which a respective phase difference (A. <p) zwischen den kohärenten laserstrahlen (102) mittels einer phaseneinstelleinrichtung (110) einstellbar ist oder eingestellt wird, die verstärkungseinrichtung(120) are amplified, wherein amplified coherent laser beams (124) are coupled out of the amplification device (120), and in which phase differences (A< / p)>

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